Glycogen Fuels Survival During Hyposmotic-Anoxic Stress in Caenorhabditis elegans

(p-ClPhSe)2 modulation on carbohydrate and lipid metabolism requires the insulin-like signaling in Caenorhabditis elegans

Organoselenium compounds modulate the metabolism by regulating carbohydrate and lipid syntheses and degradation in the liver, muscle, and adipose tissue. Notably, p-chloro-diphenyl diselenide (p-ClPhSe)2 can directly regulate the activities of enzymes involved in glucose metabolism, suggesting an insulin-like effect in rodents; however, there is still a lack of scientific evidence to confirm this hypothesis. The objective of this study was to investigate (p-ClPhSe)2 effects on glucose and lipid metabolism in Caenorhabditis elegans. The contribution of AGE-1/PI3K, AKT-1, AKT-2, PFK-1, DAF-16, and DAF-2 in the (p-ClPhSe)2 effects were also investigated. Our results demonstrate that (p-ClPhSe)2 acute exposure presented some toxicity to the worms, and therefore, lower concentrations were further used. (p-ClPhSe)2 reduced glucose and triglyceride levels to the baseline levels, after induction with glucose or fructose, in wild-type worms. This effect required proteins involved in the insulin/IGF-1 like signaling, such as the DAF-2, AGE-1, AKT-1 and AKT-2, PFK-1, but also DAF-16, which would be negatively regulated by DAF-2 activation. Moreover, the reduction in glucose and triglyceride levels, caused by (p-ClPhSe)2per se was lost in age-1/daf-16 worms, suggesting that insulin/IGF-1-like signaling in a DAF-2 and AGE-1/DAF-16 dependent-manner in C. elegans are necessary to effects of (p-ClPhSe)2. In conclusion, (p-ClPhSe)2 requires proteins involved in the IIS pathway to modulate carbohydrate and lipid metabolism.

Effects of different oxygen regimes on ecological performance and bioenergetics of a coastal marine bioturbator, the soft shell clam Mya arenaria

Benthic species are exposed to oxygen fluctuations that can affect their performance and survival. Physiological effects and ecological consequences of fluctuating oxygen are not well understood in marine bioturbators such as the soft-shell clam Mya arenaria. We explored the effects of different oxygen regimes (21 days of exposure to constant hypoxia (~4.1 kPa P_O2), cyclic hypoxia (~2.1-~10.4 kPa P_O2) or normoxia (~21 kPa P_O2)) on energy metabolism, oxidative stress and ecological behaviors (bioirrigation and bioturbation) of M. arenaria. Constant hypoxia and post-hypoxic recovery in cyclic hypoxia led to oxidative injury of proteins and lipids, respectively. Clams acclimated to constant hypoxia maintained aerobic capacity similar to the normoxic clams. In contrast, clams acclimated to cyclic hypoxia suppressed aerobic metabolism and activated anaerobiosis during hypoxia, and strongly upregulated aerobic metabolism during recovery. Constant hypoxia led to decreased lipid content, whereas in cyclic hypoxia proteins and glycogen accumulated during recovery and were broken down during the hypoxic phase. Digging of clams was impaired by constant and cyclic hypoxia, and bioirrigation was also suppressed under constant hypoxia. Overall, cyclic hypoxia appears less stressful for M. arenaria due to the metabolic flexibility that ensures recovery during reoxygenation and mitigates the negative effects of hypoxia, whereas constant hypoxia leads to depletion of energy reserves and impairs ecological functions of M. arenaria potentially leading to negative ecological consequences in benthic ecosystems.

Effect of gluten on the digestive tract and fat body of Telodeinopus aoutii (Diplopoda)

Adult specimens or larvae of invertebrates used as food for vertebrates are often maintained close to gluten so they might become vectors for cereal proteins. However, the tissues and internal organs can respond differently in animals with different feeding habits. The midgut epithelium might be a first and sufficient barrier preventing uptake and effects of gluten on the whole body, while the fat body is the main organ that accumulates different xenobiotics. Good models for such research are animals that do not feed on gluten-rich products in their natural environment. The project's goal was to investigate alterations in the midgut epithelium and fat body of the herbivorous millipede Telodeinopus aoutii (Diplopoda) and analyze cell death processes activated by gluten. It enabled us to determine whether changes were intensified or reversed by adaptive mechanisms. Adult specimens were divided into control and experimental animals fed with mushrooms supplemented with gluten and analyzed using transmission electron microscopy, flow cytometry, and confocal microscopy. Two organs were isolated for the qualitative and quantitative analysis: the midgut and the fat body. Our study of the herbivorous T. aoutii which does not naturally feed on gluten containing diet showed that continuous and prolonged gluten feeding activates repair processes that inhibit the processes of cell death (apoptosis and necrosis) and induce an increase in cell viability.

Transcriptomic Analysis of Steinernema Nematodes Highlights Metabolic Costs Associated to Xenorhabdus Endosymbiont Association and Rearing Conditions

Entomopathogenic nematodes of the genus Steinernema have a mutualistic relationship with bacteria of the genus Xenorhabdus and together they form an antagonist partnership against their insect hosts. The nematodes (third-stage infective juveniles, or IJs) protect the bacteria from the external environmental stressors and vector them from one insect host to another. Xenorhabdus produce secondary metabolites and antimicrobial compounds inside the insect that protect the cadaver from soil saprobes and scavengers. The bacteria also become the nematodes’ food, allowing them to grow and reproduce. Despite these benefits, it is yet unclear what the potential metabolic costs for Steinernema IJs are relative to the maintenance and vectoring of Xenorhabdus. In this study, we performed a comparative dual RNA-seq analysis of IJs of two nematode-bacteria partnerships: Steinernema carpocapsae-Xenorhabdus nematophila and Steinernema. puntauvense-Xenorhbdus bovienii. For each association, three conditions were studied: (1) IJs reared in the insect (in vivo colonized), (2) colonized IJs reared on liver-kidney agar (in vitro colonized), and (3) IJs depleted by the bacteria reared on liver-kidney agar (in vitro aposymbiotic). Our study revealed the downregulation of numerous genes involved in metabolism pathways, such as carbohydrate, amino acid, and lipid metabolism when IJs were reared in vitro, both colonized and without the symbiont. This downregulation appears to impact the longevity pathway, with the involvement of glycogen and trehalose metabolism, as well as arginine metabolism. Additionally, a differential expression of the venom protein known to be secreted by the nematodes was observed when both Steinernema species were depleted of their symbiotic partners. These results suggest Steinernema IJs may have a mechanism to adapt their virulence in absence of their symbionts.

Accumulation of Glycogen and Upregulation of LEA-1 in C. elegans daf-2(e1370) Support Stress Resistance, Not Longevity

DAF-16-dependent activation of a dauer-associated genetic program in the C. elegans insulin/IGF-1 daf-2(e1370) mutant leads to accumulation of large amounts of glycogen with concomitant upregulation of glycogen synthase, GSY-1. Glycogen is a major storage sugar in C. elegans that can be used as a short-term energy source for survival, and possibly as a reservoir for synthesis of a chemical chaperone trehalose. Its role in mitigating anoxia, osmotic and oxidative stress has been demonstrated previously. Furthermore, daf-2 mutants show increased abundance of the group 3 late embryogenesis abundant protein LEA-1, which has been found to act in synergy with trehalose to exert its protective role against desiccation and heat stress in vitro, and to be essential for desiccation tolerance in C. elegans dauer larvae. Here we demonstrate that accumulated glycogen is not required for daf-2 longevity, but specifically protects against hyperosmotic stress, and serves as an important energy source during starvation. Similarly, lea-1 does not act to support daf-2 longevity. Instead, it contributes to increased resistance of daf-2 mutants to heat, osmotic, and UV stress. In summary, our experimental results suggest that longevity and stress resistance can be uncoupled in IIS longevity mutants.

Effect of the mitochondrial unfolded protein response on hypoxic death and mitochondrial protein aggregation

Mitochondria are the main oxygen consumers in cells and as such are the primary organelle affected by hypoxia. All hypoxia pathology presumably derives from the initial mitochondrial dysfunction. An early event in hypoxic pathology in C. elegans is disruption of mitochondrial proteostasis with induction of the mitochondrial unfolded protein response (UPR^mt) and mitochondrial protein aggregation. Here in C. elegans, we screen through RNAis and mutants that confer either strong resistance to hypoxic cell death or strong induction of the UPR^mt to determine the relationship between hypoxic cell death, UPR^mt activation, and hypoxia-induced mitochondrial protein aggregation (HIMPA). We find that resistance to hypoxic cell death invariantly mitigated HIMPA. We also find that UPR^mt activation invariantly mitigated HIMPA. However, UPR^mt activation was neither necessary nor sufficient for resistance to hypoxic death and vice versa. We conclude that UPR^mt is not necessarily hypoxia protective against cell death but does protect from mitochondrial protein aggregation, one of the early hypoxic pathologies in C. elegans.

PQM-1 controls hypoxic survival via regulation of lipid metabolism

Animals have evolved responses to low oxygen conditions to ensure their survival. Here, we have identified the C. elegans zinc finger transcription factor PQM-1 as a regulator of the hypoxic stress response. PQM-1 is required for the longevity of insulin signaling mutants, but surprisingly, loss of PQM-1 increases survival under hypoxic conditions. PQM-1 functions as a metabolic regulator by controlling oxygen consumption rates, suppressing hypoxic glycogen levels, and inhibiting the expression of the sorbitol dehydrogenase-1 SODH-1, a crucial sugar metabolism enzyme. PQM-1 promotes hypoxic fat metabolism by maintaining the expression of the stearoyl-CoA desaturase FAT-7, an oxygen consuming, rate-limiting enzyme in fatty acid biosynthesis. PQM-1 activity positively regulates fat transport to developing oocytes through vitellogenins under hypoxic conditions, thereby increasing survival rates of arrested progeny during hypoxia. Thus, while pqm-1 mutants increase survival of mothers, ultimately this loss is detrimental to progeny survival. Our data support a model in which PQM-1 controls a trade-off between lipid metabolic activity in the mother and her progeny to promote the survival of the species under hypoxic conditions.

Animals respond to hypoxic stress by adjusting metabolic processes to balance survival and reproduction. Here the authors identify the transcription factor PQM-1 as a metabolic regulator that balances hypoxic lipid and carbohydrate metabolism in C. elegans to limit somatic integrity and promote progeny survival.

The stress-responsive gene GDPGP1/mcp-1 regulates neuronal glycogen metabolism and survival

Maladaptive responses to stress might play a role in the sensitivity of neurons to stress. To identify novel cellular responses to stress, we performed transcriptional analysis in acutely stressed mouse neurons, followed by functional characterization in Caenorhabditis elegans. In both contexts, we found that the gene GDPGP1/mcp-1 is down-regulated by a variety of stresses. Functionally, the enzyme GDPGP1/mcp-1 protects against stress. Knockdown of GDPGP1 in mouse neurons leads to widespread neuronal cell death. Loss of mcp-1, the single homologue of GDPGP1 in C. elegans, leads to increased degeneration of GABA neurons as well as reduced survival of animals following environmental stress. Overexpression of mcp-1 in neurons enhances survival under hypoxia and protects against neurodegeneration in a tauopathy model. GDPGP1/mcp-1 regulates neuronal glycogen levels, indicating a key role for this metabolite in neuronal stress resistance. Together, our data indicate that down-regulation of GDPGP1/mcp-1 and consequent loss of neuronal glycogen is a maladaptive response that limits neuronal stress resistance and reduces survival.

Characterization of glycogen molecular structure in the worm Caenorhabditis elegans

Glycogen, a glucose homopolymer with many glucose chains, is the primary blood-sugar reservoir in many organisms. It comprises β particles (∼20 nm) which can bind together to form large α particles with a rosette morphology. When dimethyl sulfoxide (DMSO) is added to glycogen from diabetic livers, α particles break apart to β particles ('fragility'), possibly due to H-bond disruption; this is not seen in healthy livers. Glycogen α and β particles, and α-particle fragility, are observed in mammals and bacteria, and are examined here in the worm Caenorhabditis elegans, with glycogen from two C. elegans strains, cultured in normal and high-glucose conditions. There were mainly β particles, with some large α particles. Most particles were fragile in DMSO. Growing in a high-glucose medium results in more long chains and more fragility, consistent with previous observations in diabetic animal models. Why high glucose levels facilitate fragility is worthy of further investigation.

WormCat: An Online Tool for Annotation and Visualization of Caenorhabditis elegans Genome-Scale Data

The emergence of large gene expression datasets has revealed the need for improved tools to identify enriched gene categories and visualize enrichment patterns. While gene ontogeny (GO) provides a valuable tool for gene set enrichment analysis, it has several limitations. First, it is difficult to graph multiple GO analyses for comparison. Second, genes from some model systems are not well represented. For example, ∼30% of Caenorhabditis elegans genes are missing from the analysis in commonly used databases. To allow categorization and visualization of enriched C. elegans gene sets in different types of genome-scale data, we developed WormCat, a web-based tool that uses a near-complete annotation of the C. elegans genome to identify coexpressed gene sets and scaled heat map for enrichment visualization. We tested the performance of WormCat using a variety of published transcriptomic datasets, and show that it reproduces major categories identified by GO. Importantly, we also found previously unidentified categories that are informative for interpreting phenotypes or predicting biological function. For example, we analyzed published RNA-seq data from C. elegans treated with combinations of lifespan-extending drugs, where one combination paradoxically shortened lifespan. Using WormCat, we identified sterol metabolism as a category that was not enriched in the single or double combinations, but emerged in a triple combination along with the lifespan shortening. Thus, WormCat identified a gene set with potential. phenotypic relevance not found with previous GO analysis. In conclusion, WormCat provides a powerful tool for the analysis and visualization of gene set enrichment in different types of C. elegans datasets.

DAF-16/FoxO in Caenorhabditis elegans and Its Role in Metabolic Remodeling

DAF-16, the only forkhead box transcription factors class O (FoxO) homolog in Caenorhabditis elegans, integrates signals from upstream pathways to elicit transcriptional changes in many genes involved in aging, development, stress, metabolism, and immunity. The major regulator of DAF-16 activity is the insulin/insulin-like growth factor 1 (IGF-1) signaling (IIS) pathway, reduction of which leads to lifespan extension in worms, flies, mice, and humans. In C. elegans daf-2 mutants, reduced IIS leads to a heterochronic activation of a dauer survival program during adulthood. This program includes elevated antioxidant defense and a metabolic shift toward accumulation of carbohydrates (i.e., trehalose and glycogen) and triglycerides, and activation of the glyoxylate shunt, which could allow fat-to-carbohydrate conversion. The longevity of daf-2 mutants seems to be partially supported by endogenous trehalose, a nonreducing disaccharide that mammals cannot synthesize, which points toward considerable differences in downstream mechanisms by which IIS regulates aging in distinct groups.

Label-free molecular mapping and assessment of glycogen in C. elegans

Caenorhabditis elegans is an animal model frequently used in research on the effects of metabolism on organismal aging. This comes with a requirement for methods to investigate metabolite content, turnover, and distribution. The aim of our study was to assess the use of a label-free approach to determine both content and distribution of glycogen, the storage form of glucose, in C. elegans. To this end, we grew C. elegans worms under three different dietary conditions for 24-48 h, representing starvation, regular diet and a high glucose diet, followed by analysis of glycogen content. Glycogen analysis was performed on fixed individual whole worms using Raman micro-spectroscopy (RMS). Results were confirmed by comparison with two conventional assays, i.e. iodine staining of worms and enzymatic determination of glycogen. RMS was further used to assess overall lipid and protein content and distribution in the same samples used for glycogen analysis. Expectedly, both glycogen and lipid content were highest in worms grown on a high glucose diet, lower in regularly fed, and lowest in starved nematodes. In summary, RMS is a method suitable for analysis of glycogen content in C. elegans that has the advantage over established methods that (i) individual worms (rather than hundreds per sample) can be analyzed, (ii) glycogen distribution can be assessed at subcellular resolution and (iii) the distribution patterns of other macromolecules can be assessed from the same worms. Thus, RMS has the potential to be used as a sensitive, accurate, cost-effective and high throughput method to evaluate glycogen stores in C. elegans.

Assessment of the behaviour and survival of nematodes under low oxygen concentrations

Oxygen is required for the completion of almost all known metazoan lifecycles, but many metazoans harbour abilities to withstand varying degrees and periods of hypoxia. Caenorhabditis elegans, one of the most popular model organism is extensively used as a model for the study of hypoxia and anoxia biology and it has been found that this nematode is capable of tolerance to varying degrees of hypoxia. Considering the extremely high diversity of nematodes, the effects of low oxygen concentration and mechanisms of adaptation to oxygen depletion differ among species. In this study, we used a simple assay to examine anoxia tolerance in four nematode species, including three free-living and one plant parasitic nematode. We found that the plant parasitic nematode Bursaphelenchus xylophilus can survive more than 14 days under anoxic conditions. Comparisons of behaviour during anoxia induction and the repertoire of oxygen sensation genes among the tested species suggested the existence of different oxygen sensation systems between B. xylophilus and C. elegans, which quickly introduce suspended animation in response to oxygen depletion to survive long-term anoxia.

Metabolic shift from glycogen to trehalose promotes lifespan and healthspan in Caenorhabditis elegans

As Western diets continue to include an ever-increasing amount of sugar, there has been a rise in obesity and type 2 diabetes. To avoid metabolic diseases, the body must maintain proper metabolism, even on a high-sugar diet. In both humans and Caenorhabditis elegans, excess sugar (glucose) is stored as glycogen. Here, we find that animals increased stored glycogen as they aged, whereas even young adult animals had increased stored glycogen on a high-sugar diet. Decreasing the amount of glycogen storage by modulating the C. elegans glycogen synthase, gsy-1, a key enzyme in glycogen synthesis, can extend lifespan, prolong healthspan, and limit the detrimental effects of a high-sugar diet. Importantly, limiting glycogen storage leads to a metabolic shift whereby glucose is now stored as trehalose. Two additional means to increase trehalose show similar longevity extension. Increased trehalose is entirely dependent on a functional FOXO transcription factor DAF-16 and autophagy to promote lifespan and healthspan extension. Our results reveal that when glucose is stored as glycogen, it is detrimental, whereas, when stored as trehalose, animals live a longer, healthier life if DAF-16 is functional. Taken together, these results demonstrate that trehalose modulation may be an avenue for combatting high-sugar-diet pathology.

Lipid and Carbohydrate Metabolism in Caenorhabditis elegans

Lipid and carbohydrate metabolism are highly conserved processes that affect nearly all aspects of organismal biology. Caenorhabditis elegans eat bacteria, which consist of lipids, carbohydrates, and proteins that are broken down during digestion into fatty acids, simple sugars, and amino acid precursors. With these nutrients, C. elegans synthesizes a wide range of metabolites that are required for development and behavior. In this review, we outline lipid and carbohydrate structures as well as biosynthesis and breakdown pathways that have been characterized in C. elegans We bring attention to functional studies using mutant strains that reveal physiological roles for specific lipids and carbohydrates during development, aging, and adaptation to changing environmental conditions.

Lifespan extension in Caenorhabditis elegans insulin/IGF-1 signalling mutants is supported by non-vertebrate physiological traits

The insulin/IGF-1 signalling (IIS) pathway connects nutrient levels to metabolism, growth and lifespan in eukaryotes ranging from yeasts to humans, including nematodes such as the genetic model organismCaenorhabditis elegans. The link between ageing and the IIS pathway has been thoroughly studied inC. elegans; upon reduced IIS signalling, a genetic survival program is activated resulting in a drastic lifespan extension. One of the components of this program is the upregulation of antioxidant activity but experiments failed to show a clear causal relation to longevity. However, oxidative damage, such as protein carbonyls, accumulates at a slower pace in long-livedC. elegansmutants with reduced IIS. This is probably not achieved by increased macroautophagy, a process that sequesters cellular components to be eliminated as protein turnover rates are slowed down in IIS mutants. The IIS mutantdaf-2, bearing a mutation in the insulin/IGF-1 receptor, recapitulates the dauer survival program, including accumulation of fat and glycogen. Fat can be converted into glucose and glycogenviathe glyoxylate shunt, a pathway absent in vertebrates. These carbohydrates can be used as substrates for trehalose synthesis, also absent in mammals. Trehalose, a non-reducing homodimer of glucose, stabilises intracellular components and is responsible for almost half of the lifespan extension in IIS mutants. Hence, the molecular mechanisms by which lifespan is extended under reduced IIS may differ substantially between phyla that have an active glyoxylate cycle and trehalose synthesis, such as ecdysozoans and fungi, and vertebrate species such as mammals.

Glycogen: A must have storage to survive stressful emergencies

Mechanisms of adaptation to acute changes in osmolarity are fundamental for life. When exposed to hyperosmotic stress, cells and organisms utilize conserved strategies to prevent water loss and maintain cellular integrity and viability. The production of glycerol is a common strategy utilized by the nematode Caenorhabditis elegans (C. elegans) and many other organisms to survive hyperosmotic stress. Specifically, the transcriptional upregulation of glycerol-3-phosphate dehydrogenase, a rate-limiting enzyme in the production of glycerol, has been previously implicated in many model organisms. However, what fuels this massive and rapid production of glycerol upon hyperosmotic stress has not been clearly elucidated. We have recently discovered an AMPK-dependent pathway that mediates hyperosmotic stress resistance in C. elegans. Specifically, we demonstrated that the chronic activation of AMPK leads to glycogen accumulation, which under hyperosmotic stress exposure, is rapidly degraded to mediate glycerol production. Importantly, we demonstrate that this strategy is utilized by flcn-1 mutant C. elegans nematodes in an AMPK-dependent manner. FLCN-1 is the worm homolog of the human renal tumor suppressor Folliculin (FLCN) responsible for the Birt-Hogg-Dubé neoplastic syndrome. Here, we comment on the dual role for glycogen in stress resistance: it serves as an energy store and a fuel for osmolyte production. We further discuss the potential utilization of this mechanism by organisms in general and by human cancer cells in order to survive harsh environmental conditions and notably hyperosmotic stress.

Adaptation to Temporally Fluctuating Environments by the Evolution of Maternal Effects

All organisms live in temporally fluctuating environments. Theory predicts that the evolution of deterministic maternal effects (i.e., anticipatory maternal effects or transgenerational phenotypic plasticity) underlies adaptation to environments that fluctuate in a predictably alternating fashion over maternal-offspring generations. In contrast, randomizing maternal effects (i.e., diversifying and conservative bet-hedging), are expected to evolve in response to unpredictably fluctuating environments. Although maternal effects are common, evidence for their adaptive significance is equivocal since they can easily evolve as a correlated response to maternal selection and may or may not increase the future fitness of offspring. Using the hermaphroditic nematode Caenorhabditis elegans, we here show that the experimental evolution of maternal glycogen provisioning underlies adaptation to a fluctuating normoxia-anoxia hatching environment by increasing embryo survival under anoxia. In strictly alternating environments, we found that hermaphrodites evolved the ability to increase embryo glycogen provisioning when they experienced normoxia and to decrease embryo glycogen provisioning when they experienced anoxia. At odds with existing theory, however, populations facing irregularly fluctuating normoxia-anoxia hatching environments failed to evolve randomizing maternal effects. Instead, adaptation in these populations may have occurred through the evolution of fitness effects that percolate over multiple generations, as they maintained considerably high expected growth rates during experimental evolution despite evolving reduced fecundity and reduced embryo survival under one or two generations of anoxia. We develop theoretical models that explain why adaptation to a wide range of patterns of environmental fluctuations hinges on the existence of deterministic maternal effects, and that such deterministic maternal effects are more likely to contribute to adaptation than randomizing maternal effects.

FLCN and AMPK Confer Resistance to Hyperosmotic Stress via Remodeling of Glycogen Stores

Mechanisms of adaptation to environmental changes in osmolarity are fundamental for cellular and organismal survival. Here we identify a novel osmotic stress resistance pathway in Caenorhabditis elegans (C. elegans), which is dependent on the metabolic master regulator 5'-AMP-activated protein kinase (AMPK) and its negative regulator Folliculin (FLCN). FLCN-1 is the nematode ortholog of the tumor suppressor FLCN, responsible for the Birt-Hogg-Dubé (BHD) tumor syndrome. We show that flcn-1 mutants exhibit increased resistance to hyperosmotic stress via constitutive AMPK-dependent accumulation of glycogen reserves. Upon hyperosmotic stress exposure, glycogen stores are rapidly degraded, leading to a significant accumulation of the organic osmolyte glycerol through transcriptional upregulation of glycerol-3-phosphate dehydrogenase enzymes (gpdh-1 and gpdh-2). Importantly, the hyperosmotic stress resistance in flcn-1 mutant and wild-type animals is strongly suppressed by loss of AMPK, glycogen synthase, glycogen phosphorylase, or simultaneous loss of gpdh-1 and gpdh-2 enzymes. Our studies show for the first time that animals normally exhibit AMPK-dependent glycogen stores, which can be utilized for rapid adaptation to either energy stress or hyperosmotic stress. Importantly, we show that glycogen accumulates in kidneys from mice lacking FLCN and in renal tumors from a BHD patient. Our findings suggest a dual role for glycogen, acting as a reservoir for energy supply and osmolyte production, and both processes might be supporting tumorigenesis.